Cable modems are often used to provide broadband services over cable television networks. The cable modem interconnects end user devices to a coaxial cable that transmits data to a cable modem termination system (CMTS). Cable modems are usually located in a customer's premises and frequently they are in part managed by end users. Thus, cable service providers do not usually have complete control of the cable modems connected to their systems.
Cable service providers sometimes experience theft of service. The theft is frequently accomplished by use of “cloned” cable modems. Cable modems can be cloned in many ways. A common method is to clone a cable modem's media access control (MAC) address. A MAC address is a globally unique address associated with networking hardware. A cable modem that only duplicates a MAC address from another cable modem is often called a simple clone. Since legitimate MAC addresses are unique for each piece of hardware, service providers often manage services based on the MAC addresses. This makes it possible for someone to steal cable service by duplicating a MAC address from a cable modem that is legitimately provisioned for service.
Cable modems can be cloned in various other ways than by merely copying the MAC address. For example, a modem may be cloned by copying the firmware, service profiles, or the baseline privacy interface (BPI) certificates. When more than just the MAC address of a modem is cloned, the cloned cable modem is often referred to as a perfect clone.